Abstract:

Particle suspensions in turbulent flows occur in nature and industry. In many situations, the particles have a density different from that of the carrier fluid. This density difference can affect their motion through flows, and offers potential for changing the drag as well as the transport of various quantities in multiphase flows. In this talk, we will discuss the use of particle-tracking techniques to study the dynamics of light (buoyant) particles in homogeneous isotropic turbulent flows. We will begin with the acceleration dynamics of tiny buoyant particles (100 micron bubbles in water), with a very small Stokes number (St), where St signifies the particle’s response-time in the flow. We address the question: Can a small particle with a very small Stokes number be regarded a good tracer of the flow? Our analysis shows that gravity can lead to modification of both vertical and horizontal acceleration statistics, and these occur despite the small size and minute St of these particles. Some implications of these findings to dispersed particle-laden flows in the oceans and the atmosphere will also be discussed. We then address the motion of buoyant particles of finite-size (particle size is large compared to the smallest turbulent flow length-scales). For these particles, buoyancy is seen to produce interesting variability in dynamics. We will present the effect of changing the Galileo number on particle dynamics, and also touch upon some interesting effects of changing the particle’s moment of inertia.

Brief Biograph:

Dr. Varghese Mathai obtained his PhD in 2017 from the Physics of Fluids group at the University of Twente, where is postdoc now. Prior to this, he did his Masters in Mechanical Engineering from the Indian Institute of Science, Bangalore. He was at General Electric co., Bangalore for 2 years, where he worked on fuel sprays and flows in aircraft engines. His research interests include particle- and bubble-laden turbulent flows, wake-induced-vibrations, and free surface flows. He will mainly talk about the dynamics buoyant particles in turbulent flows.

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